We didn’t see the movie until after having read Book 7.
I was disappointed in the movie; unlike Goblet of Fire, where the book was bloody awful (worst book in the series by a considerable margin), I didn’t go into this movie with lowered expectations.
I did expect them to have to edit the hell out of it; it’s a huge book. They could’ve made an all-fall miniseries out of it and gone with 6 hours’ worth of screen time and still found it necessary to chop out some of what was in that book. But the editing was pretty awful. Rather than select a handful of subplots and handle them well, and bracket the rest off as much as possible, the movie skims along the surface of a double handful thereof and leaves many of them as unfinished business, with the net effect that those subplots just don’t work in the movie.
The most egregious of these is Hogwards School of Magic finally turning on Umbridge after she’s assumed Dumbledore’s position. A very watered-down & incomplete face-off between Umbridge and McGonagall (that stole what should’ve been Maggie Smith’s best screen time of the series), and a Fred & George scene that gets aborted just as it’s getting going good by Harry getting visions of Sirius in trouble.
But spotty jobs were also done on: the Snape/Harry conflict over occlumency; Harry’s angst-y alienation from Ron and Hermione; the prophecy, and why Voldie gives a rat’s ass; and Kreacher vs Sirius (and versus the Order in general) including the betrayal.
Nevertheless, lots of good scenes and good plot development:
Umbridge, as noted, excellent, well played and well cast;
The Dumbledore’s Army, training, etc; they had enough of Harry’s isolation prior to that point to make it work, good job
The final fight in the Ministry: excellent, superlative when it was the kids versus the Death Eaters; a bit confusing when the adult Order shows up (at that point they were trying to do too many thing simultaneously), but all in all better than the book, as others have already said.
Fudge: well done, a fearful nay-sayer who is out to get Harry yet without being a Voldemort stooge. Inept and corrupt, but not volitionally evil. “He’s back!!”. heh.
I liked the movie better than Goblet, and I think better than the first movie Sorcerer’s Stone, but definitely not as much as Prisoner of Azkaban and not really as much as Chamber of Secrets.
I think an extra 45 minutes’ worth of footage (and not, dammit, devoted to yet more special effects) would have really propelled this movie out of the mixed-bag zone. They cut too much muscle meat off the bone for it to really work, though.